Hydraulic timing means



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y 17, 1955 J. v. BRADY ETAL 2,708,354

' HYDRAULIC TIMING MEANS,

Filed June 5, 1952 s Sheets-Sheet 1 INVENTORS. Jcwnea' K15324241 B ZZZfiMZ y 7 1955 J. v. BRADY ETAL 2,708,354

HYDRAULIC TIMING MEANS y 17, 1955 J. v. BRADY ETAL 2,708,354

HYDRAULIC TIMING MEANS Filed June 5. 1952 5 Sheets-Sheet 3 INVENTORS.Jamzea l BYZ/Zmffi I M M17 MQM United States Patent HYDRAULIC TIMINGMEANS James V. Brady, New York, N. Y., and William I. Hamilton,Hackensaek, N. J., assignors to Lanova Corporation, Long Island Cit N.Y., a corporation of Belaware Application June 3, 1952, Serial No.291,412

4 Claims. (Cl. 6425) This invention relates to means for varying theangular relation between a drive shaft and a shaft driven thereby, fortiming the injection or admission of fuel in internal combustionengines, and analogous purposes.

Injection or diesel engines are quite sensitive to the timing of theinjection of fuel. It is desirable for most efiicient operation ofinjection engines, particularly engines operating over a Wide speedrange, to advance and retard the injection timing in accordance withincrease and decrease in engine speed. Injection timing devices areknown. In general, the known devices are rather complicated andexpensive in construction, lack sensitiveness in operation and often areinadequately lubricated.

Our invention is directed to means for varying the angular relationbetween a drive shaft and a shaft driven thereby, particularly suitablefor use as injection timing means, but suitable also for other purposes.The drive shaft has driving connection to the driven shaft through ahydraulic servo-motor effective for varying the angular relation betweenthe shafts. As used with injection engines, the drive shaft is drivenfrom the engine shaft, the driven shaft is the operating or cam shaft ofthe injection pump, and the servomotor is controlled by valve means. Thevalve means is adjustable responsive to the speed of the drive shaft, toprovide automatic adjustment of injection timing. The control valvemeans comprises a control valve adjustable relative to the housing andthe rotor of the servo-motor, the rotor being turnable relative to thehousing and the control valve. The latter and a sleeve valve turnablewith the rotor, and the drive shaft, are provided with cooperating portsand ducts or passages for admitting and discharging operating hydraulicfluid to and from the servo-motor effective for turning the rotor inproper direction to an appropriate extent for effecting and maintainingdesired angular adjustment of the driven or pump cam shaft relative tothe drive shaft. Conveniently, the operating hydraulic fluid is theengine lubricating oil delivered by the usual oil pump from the enginecrank case sump to the servo-motor under substantial pressure. Theservo-motor is provided with means for preventing clogging thereof bydirt contained in the oil and is also provided with means guardingagainst movement of the rotor relative to the housing due to variationsin torque required to drive the injection pump shaft, which is maximumat the instant of injection and then rapidly falls to a minimum. All ofthe moving parts of the servo-motor and the control valve and associatedparts operate in oil so that no appreciable friction occurs, which isconducive to sensitiveness and accuracy in operation. Further objectsand advantages of our invention will appear from the detail description.

In the drawings:

Figure 1 is a lengthwise central vertical sectional view, takensubstantially on line 1-1 of Figure 2, of injection timing meansembodying our invention, certain parts being shown in elevation andcertain other parts being shown partly in elevation and partly brokenaway and in section, the injection pump being shown fragmentarily andthe sleeve valve turnable with the rotor.

parts being shown in the positions which they occupy when the injectionpump cam shaft is in full retard position;

Figure 2 is an end view of the timing means of Figure 1, with thehousing cover plate removed and the housing shown fragmentarily, withthe parts in the positions which they occupy when the cam shaft of theinjection pump is in full retard position;

Figure 3 is a sectional view taken substantially on line 33 of Figure 1;

Figure 4 is a sectional view taken substantially on line 44 of Figure 1;

Figure 5 is a sectional view taken substantially on line 5-5 of Figure1;

Figure 6 is a sectional view taken substantially on line 6-6 of Figure1;

Figure 7 is a sectional view similar to Figure 3, but with the parts inthe positions which they occupy at advanced position of the injectionpump cam shaft;

Figure 8 is a sectional view similar to Figure 4, but with the parts inthe positions which they occupy at advanced position of the pump camshaft;

Figure 9 is a sectional view similar to Figure 4, but with the parts inthe positions which they occupy when the injection pump shaft is inretard position; and

Figure 10 is a sectional view similar to Figure 3, but with the controlvalve and the other parts in the positions which they occupy in Figure9.

Our instant invention is in the nature of an improvement over thehydraulic timing means of the copending application of James V. Brady,Serial No. 255,891, filed November 6, 1951. in the timing means of ourinstant invention admission of oil to, and drainage of oil from, theservo-motor is controlled by the control valve and a The control valveis piloted in the sleeve valve, the latter is piloted in the head of thedrive shaft, and the passages or ducts for supplying oil to, anddraining oil from, the servo-motor are in the head of the drive shaft.With that arrangement, but two ports and a groove, in the control valve,and four ports, in the sleeve valve, are required, regardless of thenumber of vanes on the rotor. That is conducive to accuracy in indexingof the ports in the control valve and in the sleeve valve, which is ofimportance. Further, the passages or ducts for supplying oil to, anddischarging -=,oil from, the servo-motor are arranged in two groups,

those of one group opening into a common channel in the head of thedrive shaft and those of the other group opening into another andseparate channel in the head of the drive shaft. That avoids necessityfor precision in ,drilling the passages or ducts in the head of thedrive shaft, thereby reducing expense and assuring accuracy inoperation. An additional and important advantage of our invention isthat the control valve and the drive shaft may be quite short so thatpossibility of bending and binding of parts, due to any slightmisalignment or distortion, such as might be caused by the drive gearthrust, is effectively guarded against. That eliminates binding andobjectionable wear of parts and renders it possible to reduce clearancesto a minimum thereby reducing oil leakage to a minimum, which isconducive to sensitivity and accuracy in operation.

The timing means of our invention is particularly suitable for use withinjection engines and will be so described, though in its broaderaspects it may be used for other purposes, as above noted. We have shownthe timing means of our invention, by way of example, as used with aninjection pump 2%, which may be any suitable known purnp, having acasing 21 and an operating A cylindrical casing 24 is bolted to one endof the pump outer end of collar casing 21, about annular flange 25thereof, with an intervening sealing O ring 26. The casing 24 is coaxialwith cam shaft 22 and is bolted at its other end to an inner plate 27 ofa casing 28 which extends upwardly from and opens downwardly into thecrank case (not shown) of an injection engine with which the injectionpump 29 is associated. The casing 2-8 is provided with a front wall orplate 29 having a circular opening therein about which is disposed anannular collar fill on theouter end of which seats a cover plate 31,this plate 31 and collar 39 being bolted or otherwise suitabl secured tofront wall 29 of casing 23.

The outer end wall 33 of casing 23% is thickened and is provided with anoutwardly extending annular flange 34 about which plate 27 seats, withan axial bore in which is mounted a bearing bushing 35. A tubular driveshaft 36 is rotatably mounted through bushing and is, provided withradial inlet ports 37 opening interiorly thereof and opening at theirouter ends into an interior circumferential groove 38 in the bushing 35.The shaft 36 extends outward beyond plate 27 and has its outerend'portion slightly reduced in diameter to provide a shoulder againstwhich seats a flanged collar 49 keyed on shaft 32: and restrainedagainst outward movement thereon by a thimble ili threaded into theouter end of shaft 36 and provided at its outer end with a head 42,there being .a washer 43 confined between head 42 and the A gear 44seats on flange 45 of collar 4 and is suitably secured thereto,conveniently by bolts 46. This gear 44, in practice, is driven, throughsuitable gearing,from the engine crank shaft so that the shaft 3: isdriven at predetermined speed relative to the engine crank shaft,- as isknown.

The bolts 46 pass through an annular clamping and reinforcing plate 48seating on the web of gear 44 and, in cooperation with the belts in,clamping it tightly against flange 45. A substantially oblong arm i9 iskeyed on the outer end of a control valve mounted for relative turningmovement in drive shaft 36 and extending outward therebeyond. The arm 59is recessed at its midlen'gth for reception of a spring washer 51confined between arm and head 52 of a cap screw 53 threaded into theouter end of control valve portion of control valve 5% is slightlyreduced in diam-. eter, as shown in Figure l, to provide a shoulderbetween which and the washer 51 arm 49 is confined. Two oppositelydisposed fly weights 5'4, shown more clearly in Figure 2, are pivoted attheir outer ends, at 55, on the clamping plate 48, the studs or pivots55 being secured to plate 48 andprojecting an appropriate distanceoutward therebeyond. Posts 56 are pivotally mounted on Weights 54radially inward thereof beyond the pivot studs 55and a tension spring 57extends between and is anchored at its ends to the posts 56. Pins 58 aresecured in the'fly weights 54, adjacent the ends thereof remote from thepivot studs 55, and extend through oppositely disposed cam slots 59 inthe end portions of arm 49. As will be understood from what has beensaid, the tension spring 57 urges the fly weights 54 toward each otherand,

when the drive shaft 36 is not rotated, or is rotated at a speedcorresponding to or less than the full retard angular position of thepump cam shaft 22 relative to drive shaft 36, as will be explained morefully later, pulls the fly weights54 into their innermost positions,with the pins 58 at the inner ends of the cam slot 59, as shown inFigure 2. When the speed of rotation of drive shaft 36 is increased toor beyond a predetermined value, which may be termed its advanceinjection speed, as will be ex plained more fully later, the fly weights54 swing outward in opposition tothe tension spring 57 and the pins 58,in cooperation with the cam slots 59, turn thearrn 49 and thereby turnthe control valve 58. The cam slots 59 are so disposed that unit 49 isturned clockwise, as viewed in Figure 2, by outward movement of fly'weights 54 and is turned counterclockwise by inward movement thereof.Accordingly, the control valve 50 is turned clockwise responsive toincrease in speed of rotation of the drive shaft 36 and is turnedcounterclockwise responsive to decrease in the speed of rotation ofdrive shaft 36, within the speed range thereof from full retardinjection to full advance injection.

The control valve 50 is provided with an outer circumferential shoulder61 confined between the inner end of thimblc 41 and an interior shoulderof shaft 36, effective for restraining control valve 55) against endwisemovement in either direction while permitting free turning thereofwithin shaft 36. A plug 62 is threaded into and closes the inner end ofa bore in the control valve 50 extending from the inner end thereof,providing an admission chamber 63 for operating hydraulic fluid, as willbe explained more fully later. The control valve 50 is provided with areduced bore or inlet duct 64 extending from the outer end of chamber 63and with inlet or admission ports d5 opening radially outward from duct64 into an annular space (it) surrounding control valve 56), as willappear more fully later.

The bearing bushing is provided with an admission port 67 which opensinto an admission passage 65 in end wall 33 of casing 24. The outer endportion of passage 68 is enlarged and threaded to receive the threadedend portion of a tube 69 connected to a suitable source of The outer endi supply of operating. hydraulic fluid under appropriate pressure. inpractice, the tube 69 is connected to the discharge of an oil pump ofsuitable known type, which withdraws oil from the sump of the enginecrank case and delivers it under appropriate pressure to tube 69.Referring further to Figure l, the inner end of admission duct 6-; isformed to provide a seat for a ball check valve '70 urged in closingdirection by a compression spring 71 confined between valve 79 and plug62, for a purpose which will be described later.

The drive shaft 36 is provided, at its inner end, with, an enlargedfrusto-conical head 66 and a cylindrical head 72, comprising acylindrical body or barrel 73 within which are disposed a suitablenumber-six being shownoi' abutment elements 74 of approximately sectorshape. These abutment elements 74 fit tightly against the innercircumferential face of barrel 73, are spaced apart circumferentiallythereof and extend radially inward of barrel 73. ring 75 fits tightly inthe inner end of barrel 73 and is secured therein by bolts 76 passingthrough head 66 and through the abutment elements 74 and threading intoplate 75. The barrel 73 is positioned axially by flanges 77 and 73 ofhead 66 and plate 75, respectively, and abutment elements 74 are clampedtightly between plate 75 and head 66 and are held accurately in positionthereby and by the bolts 7 6.

The head 72 provides a cylindrical housing closed at its ends forreception of a rotor 30 shown more clearly in Figures 1 and 6. Thisrotor "30 comprises a central cylindrical hub 81 and vanes 82 integralwith and extending radially outward from hub 51 into the spaces 83between the abutment elements 74. The outer end of hub 81 of rotor 89has a sealing, but not tight, fit against the flat inner face of head 66of drive shaft 36. Hub 81 also has a sealing, but not tight, fit betweenthe inner ends of the abutment elements 74, and the inner end of hub 81has a sealing, but not tight, fit against the fiat.

outer face of the end closure plate 75. The vanes 82 of rotor 36 are ofsubstantially less thickness than the width of the spaces 83 between theabutment'elements' 74 and have a sealing, but not tight, fit with thecircumferential wall of barrel 73 and with the inner face of 7 cap screwBlthreaded into the end of cam shaft 22, there An annular flangedclosure plate or 33 being a retaining ring 92 and a lock washer 93, ofsuitable known type, confined between me head of screw 91 and aninterior shoulder of hub 81 for restraining the latter against outwardmovement lengthwise of cam shaft 22, hub 31 being restrained againstinward movement by the inner race of the ball bearing 23, as will beclear from Figure l. The hub 81 is provided with suitably disposeddischarge ducts 94 extending therethrough from the inner end of chamber85 of rotor 8%, for discharge of the hydraulic operating fiuid or oilfrom chamber 85 into the l casing 24, as will appear more fully later.The oil is discharged from the lower portion of casing 2-7? through anopening 95 in end wall 33 of casing 24 and thence downward throughcasing 2-3 into the crank case of the engine.

The frusto-conical head 66 of drive shaft 36 is provided with a firstset of substantially radial ducts 98 with their radially outer endsopening through the inner face of head 66 at one side of the vanes 82into the spaces 33 between the abutment elements 7%. Head 66 is furtherprovided with a second set of substantially radial ducts 101 with theirradially outer ends opening through the inner face of head 66 into thespaces 83 between the abutment elements '74 and at the sides of vanes 82opposite to those at which the ducts 93 are located.

The drive shaft 36 is bored out from its inner end to receive a sleevevalve 86 fitting snugly, but not tightly, in shaft 36 and over the innerend portion of control valve 59, the latter being piloted in sleevevalve 86 and sleeve valve 85 being piloted in shaft 36 with the latterpiloted thereon. The sleeve valve 86 is provided with two upper ports 87and 88 and two lower ports 89 and 99, spaced apart lengthwise thereof.The ports 87 and 89 open into an inner circumferential channel 96 inhead 66 of drive shaft 36, and the ports 88 and 96 open into a secondinner circumferential channel 97 in head 66. The outer end of sleevevalve 86 is spaced from the outer end of the bore in shaft 36, toprovide the space 66 about control valve 50, previously mentioned. Thesleeve valve 86 is provided, at its inner end, with two diametricallyopposite slots S 9 and 160 which receive a key 102 fitting snuglytherein and in diametrically opposite grooves in the outer end of hub 81of rotor 89. The sleeve valve 86 is thus attached to rotor 89 forrotation therewith and is restrained against relative axial movement, byhub 31 of rotor 89 and by the pressure of the oil in space 69 on theouter end of sleeve valve 86. The slot 1% is extended so as to overlapthe inner end portion of a lengthwise drainage or discharge groove orpassage 103 in the outer face of control valve at the lower portionthereof as shown in Figure l. The groove 103 is of approximately thesame width as the respective ports 89 and 9t) and of a length to brid eboth thereof.

The control valve is further provided, at the opposite side thereof fromgroove 163, with two radial ports 1135v and 106 extending from theadmission chamber 63, disposed in the same transverse planes as thechannels 96 and 97, respectively. The abutment members 74 are providedat one side of the outer ends thereof with recesses 107 aligned with theducts or passages of head 66 of drive shaft 36, and at the oppositesides of their outer ends with recesses 168 aligned with the ducts orpassages 101, for admitting oil under pressure to the servo-motor at oneside of the vanes 82 of rotor 86 while draining oil from the other sideof vanes 82, as will be explained more fully presently.

When the drive shaft 36 is not rotating, or is being driven at a speedless than that requiring advancement of injection, the rotor 80 is inits full retard position, in which the leading faces of the abutmentelements 74 are in contact with the vanes 82 of rotor 86, it beingunderstood that the shaft 36 is driven clockwise as indicated by thearrow in Figure 2. The control valve 50 is then also in its maximumcounterclockwise or retard position and both of the ports 105 and 1%thereof are then closed at their radially outer ends by sleeve valve 86,and groove 193 is closed to ports 89 and 9t) of sleeve valve 86, bycontrol valve 58, as will be clear from Figures 3 and 4. The rotor isthen driven from the drive shaft 36 through the direct mechanicaldriving connection provided by the abutment elements '74 and the vanes82, and the angular relation between the drive shaft 36 and theinjection pump cam shaft 22 remains unaltered.

Referring to Figures 7 and 8, upon increase in speed of rotation of thedrive shaft 36 to a value requiring advancement of injection, the flyweights 54 move outward in opposition to tension spring 57, under theinfluence of centrifugal force, turning the control valve 50 inclockwise direction. This turning of the control valve 50 brings port165 into communication with port 87, while maintaining groove 163 closedto port 39. Oil then flows under pressure from the admission chamber 63into channel 96 and thence through ducts 98 into the servo-motor,between the abutment elements 74 and the vanes 82 of rotor The enteringoil exerts pressure upon the corresponding faces of the vanes 82 andturns the rotor 86 in clockwise or injection advance direction relativeto the associated housing. That advances the angularity of the injectionpump cam shaft 22 relative to the drive shaft 36 thereby advancing thetiming of injection to the desired extent corresponding to the enginespeed. When the desired advancement of injection has been eifected, theturning of sleeve valve 86 on the control valve 50 substantially closesthe radially outer end of the port 1G5, leaving it cracked slightly openfor a purpose to be described presently.

During clockwise turning of rotor 86 relative to the enclosing housing,the oil at the opposite sides of the vanes 82 from the ducts 98 isdisplaced and passes through ducts 161 into channel 97 and thencethrough port 99 and groove 1% into the outlet or discharge chamber 85 ofrotor hub 31, from which the oil flows through ducts 94 into casing orhousing 24 and is returned to the engine crank case as previouslydescribed. As will be understood, when the radially outer end of theport 195 of control valve 59 is uncovered by turning thereof, theradially outer end of the port 196 remains closed by sleeve valve 86 andgroove 103 is opened to port 9% as shown in Figure 8. If the speed ofrotation of drive shaft 36 continues to increase, the control valve 56will be turned a further distance clockwise and that may continue untilthe maximum speed of rotation of drive shaft 36 is reached and themaximum advancement of injection has been attained, at which time therotor 81 will have been turned into its maximum advance position. Whenthe rotor 80 has been turned, clockwise relative to drive shaft 36, adistance corresponding to the speed of rotation of shaft 36, withcorresponding turning of the sleeve valve 86 about control valve 56, theports and 99 are cracked open. That is desirable in order to maintainoil under appropriate pressure in the spaces between the vanes 82 andthe elements '74, in the event of slight leakage about the vanes, sincethe drive between the housing and the rotor is then through the oilconfined between the vanes 82 and elements 74. As will be understoodfrom what has been said, the rotor 89, and with it the injection pumpcam shaft 22, may be advanced to any desired extent, within limits,relative to the drive shaft 36. The rotor 38 and its enclosing housingand associated parts thus constitute a servo-motor controlled by thecontrol valve 50 and the sleeve valve 86 and responsive to the speed ofrotation of the drive shaft 36 and, therefore, responsive to enginespeed, for automatically advancing the timing of injection in accordancewith increase in speed of rotation of drive shaft 36.

When the speed of rotation of drive shaft 36 decreases,

the control valve 50 is turned counterclockwise thus opening port 106,closing groove 1% to port 99, closing port 1135, and opening the port 89to the groove 193, as shown in Figures 9 and 10. Oil then flows throughducts 191 under pressure into the servo-motor at one side of the vanes32 thus turning the rotor 86 in counterclockwise direction, the oil atthe opposite sides of the vanes being discharged through ducts 98,channel 96, port 8 and groove 1133 into the discharge chamber 85, fromwhich it is delivered into the casing 24 and thence into casing 28 anddownward into the engine crank case, as before. This counterclockwiseturning of rotor 84? reduces the angle of advancement of the injectionpump cam shaft relative to the drive shaft 36, thereby retarding thetiming of injection, as will be understood. if there is no furtherdecrease in the speed of rotation of drive shaft 36, thecounterclockwise turning of rotor 813, and with it sleeve valve 86,closes the ports 88 and 196, and closes port 8? to groove 1%, ports 37and H35 being then cracked slightly open to supply make-up oil to therotor 80 in replacement of oil which may leak past the vanes 82, andport K) also beingithen cracked slightly open to groove 103 to drain offthe oil leakage; thus maintaining the angular adjustment between theshafts 36 and 22.

If thespeed of rotation of drive shaft 36 continues to decrease, thecontinued turning movement of control valve 50 counterclockwisemaintains the ports 88 and itl open and the port S9 open to groove 1%,while maintaining ports 87 and 165 closed and port 9% closed to groove1%, until the rotor 86 is returned to full retard position, at whichtime all of the ports'lt o, fill, H35 and 89 are again closed, asbefore. 7

As will be seen, from what has been said, the servomotor, under controlof the control. valve is effective for advancing and retarding thetiming of injection responsive to increase and decrease in the speed ofrotation of the drive shaft 36, throughout the range of turning movementof the rotor 8t relative to the servo-motor housing. in general, anangular adjustment of approximately fifteen degrees of the rotor 86relative to its associated housing is sufficient, though that angle maybe varied to suit conditions. Also, by varying the cam slots 59, therate of adjustment, or advancing or retarding of the timing ofinjection, may be adjusted or set to suit any particular engine.

In the operation of the injection pump, the peak torque required occursat the instant of injection and then falls off rapidly to a rninirnum'.Accordingly, at the instant of injection there would be a tendency toforce oil from between the vanes 82 and the abutment members 74 backinto and through the admission chamber 63 of the control dirt, such ascarbon and other impurities. Such impurities are urged toward thecircumferential wall of the housing of the servo-motor, during rotationthereof, by centrifugal force, and are removed therefrom through thepassages or ducts 98 or iii} and the corresponding channels and ports ofthe drive shaft 36, sleeve valve 36 and control valve 5%, and groove M53of control valve St), as will be understood from what has been said.lnthat manner, dirt which would tend to accumulate within theservo-motor and might causeclogging thereof to such an extent as tointerfere objectionably with its accuracy in operation, iscontinuously'removed therefrom, which is conducive to accuracy in thetiming of injection, it will alsobe noted that the movable parts of theservo-motor,

including the control valve 5?, operate in oil, which elimi- 1 hatesfriction and resultant wear and further contributes that precision indrilling of those ducts is not required.

Operation of the servo-motor is controlled by but four ports in thesleeve valve 86 and two ports and the groove 14)? in control valve 56,all of which are spaced well apart and may be precisely indexed withoutdifficulty, which is conducive to accuracy in operation. Further, byprovid- 5 ing the sleeve valve 36, the drive shaft 36 may be quite shortso as to avoid risk of bending and binding of parts, thereby reducingnecessary clearance and resultant oil leakage to a minimum. 7

The timing means of our invention is particularly suitable for timingthe injection in injection engines, and has been described as used forthat purpose, by way of example. In its broader aspects, however, it maybe used for varying the angular relation between a drive shaft or memberand any driven shaft or member. Accordingly, the driven shaft may be,for example, a cam shaft for actuating the valves of an aspirationinternal combustion engine receiving fuel-air mixture from a carburetoror other suitable source, or any other shaft or member which it isdesirable to adjust for timing purposes.

As above indicated, and as will be understood by those skilled in thisart, changes in detail may be resorted to. without departing from thefield and scope of our invention, and we intend to include all suchvariations, as fall within the scope of the appended claims, in thisapplication in which the preferred form only of our invention has beendisclosed.

We claim:

1. lrrmeans for varying the angular relation between two shafts, adriven shaft, a tubular drive shaft coaxial with said driven shaft, aservo-motor providing driving connection between said shafts comprisinga housing fixed to said drive shaft and a rotor within said housingfixed to said driven shaft, said housing having circumferentially spacedabutment elements fixed thereto extending in- Wardly thereof, said rotorhaving vanes extending between said elements, said drive'shaft havingtwo interior inwardly opening circumferential channels spaced apartaxially thereof and two sets of ducts respectively opening into saidchannels, the ducts of one set opening into said housing at one side ofsaid vanes and the ducts of the other set opening into said housing atthe other side of said vanes, a control valve concentric with said driveshaft turnable relative thereto and having a discharge passage, and asleeve valve cooperating with said control valve concentric with saiddrive shaft and turnable with said rotor about said control valve, saidvalves having cooperating ports effective for admitting operatinghydraulic fiuid to one of said channels and connecting the other thereofto said discharge passage and vice versa responsive to turning of saidcontrol valve in one direction and in the other direction respectivelyrelative to said drive shaft.

2. In means for varying the angular relation between two shafts, adriven shaft, a tubular drive shaft coaxial with said driven shaft, aservornotor providing riving connection between said shafts comprising ahousing fixed to said drive shaft and a rotor within said housing fixedto said driven shaft, said housing having circumferentially spacedabutment elements fixed thereto extending in-. wardly thereof, saidrotor having vanes extending between said elements, said driveshafthaving two interior inwardly opening circumferential channelsspaced apart axially thereof and two sets of ducts respectively openinginto said channels, the ducts of one set openinginto said housing at oneside of said vanes and the ducts of the other set opening into saidhousing at theother side of said vanes, a control valve concentric withsaid drive shaft turnable relative thereto and having an admissionchamber and a discharge passage, and a sleeve valve con centric withsaid drive shaft and turnable with said rotor about said control valve,said valves having cooperating ports effective for opening one of saidchannels to said chamber while closing it to said passage and closingthe other of said channels to said chamber while'opening it to 9 saidpassage and vice versa responsive to turning of said control valve inone direction and in the other direction respectively relative to saiddrive shaft.

3. In means for varying the angular relation between two shafts, adriven shaft, a tubular drive shaft coaxial with said driven shaft, aservomotor providing driving connection between said shafts comprising ahousing fixed to said drive shaft and a rotor within said housing fixedto said driven shaft, said housing having circumferentially spacedabutment elements fixed thereto extending inwardly thereof, said rotorhaving vanes extending between said elements, said drive shaft havingtwo interior inwardly opening circumferential channels spaced apartaxially thereof and two sets of ducts respectively opening into saidchannels, the ducts of one set opening into said housing at one side ofsaid vanes and the ducts of the other set opening into said housing atthe other side of said vanes, a control valve in said drive shaftconcentric therewith turnable relative thereto and having an interioradmission chamber and an exterior discharge passage, and J a sleevevalve fitting in said drive shaft and about said control valve andturnable with said rotor about said control valve, said valves havingcooperating ports effective for opening one of said channels to saidchamber While closing it to said passage and closing the other of saidchannels to said chamber while opening it to said passage and vice versaresponsive to turning of said control valve in one direction and in theother direction respectively relative to said drive shaft.

4. In means for varying the angular relation between two shafts, twocoaxial shafts, a servo-motor providing driving connection between saidshafts comprising a housing fixed to one of said shafts and a rotorwithin said housing fixed to the other shaft and turnable in eitherdirection relative to said housing, said one shaft being tubular and hving two interior inwardly opening circumferential channels spaced apartaxially thereof and two sets of ducts respectively opening into saidchannels for admitting and exhausting operating fluid to and from saidhousing, a control valve in said one shaft concentric therewith turnablerelative thereto and having an interior admission chamber and anexterior discharge passage, and a sleeve valve fitting in said one shafteffective for closing the inner sides of said channels and fitting aboutsaid control valve and turnable thereabout with said rotor, said valveshaving cooperating ports effective for opening one of said channels tosaid chamber while closing it to said passage and closing the other ofsaid channels to said chamber while opening it to said passage and viceversa, responsive to turning of said control valve in one direction andin the other direction respectively relative to said one shaft.

References Cited in the file of this patent UNITED STATES PATENTS2,488,361 Witzky et a1 Nov. 15, 1949 FOREIGN PATENTS 467,808 GreatBritain June 23 ,1937

561,811 Great Britain June 6, 1944

